At some point in the best meals there's a sweet spot when a mouthful makes you inexplicably happy. The food writer Trish Deseine wonders at it. How does great food travel so quickly to your eyes and make you see things in a better light?

We both take in the room from comfy leather chairs that seem designed for that sit-back-and-smile moment.

Trish is visiting from France on a grand food tour of Ireland. We've never met. But for the hell of it I tweeted her a few days earlier to see if she could join me at the country's poshest and (according to the Michelin guide) best place to eat: Restaurant Patrick Guilbaud, Ireland's only two-star restaurant, in Dublin's Merrion Hotel.

She has never eaten here. It is (yikes) 25 five years since I did. I was leaving my first job to go to England, and have a vivid memory of the moment when the waiters stood behind each of our seats and a hush fell. Every eye in the place turned to look. On cue they each lifted a polished silver cloche off our dinner plates. I don’t remember what I ate but it tasted unlike anything I’d eaten before. “Was it an epiphany?” Trish asks. Not really. I was 19 and mortified purple by this palace of preciousness.

A working trip to Restaurant Patrick Guilbaud has shades of a beauty editor cracking open a bottle of Chanel No 5. Is it a curtsey to Dublin’s restaurant royalty, a place we know is good because for these prices it bloody should be? My plan is to stick to the set lunch, at €50 a head. It’s a sum you can easily drop for an un-starred meal. So I hand back the tome of a wine list, which weighs roughly a kilo, and ask for a wine by the glass recommendation.

We have been swept through the vaulted room to our corner table on a murmuration of suited waitstaff. Chairs are moved to catch us as we sit. Crumbs will be swept.

The dining room is surprisingly quiet for a Friday lunch, but seems to fill as the afternoon goes on. No-one looks like they’re here on an expense account. At a time when most businessmen are working on their tans Monsieur Guilbaud is working the room.

First up, an amuse bouche of silky creamed potato with a fluffy orange grating of Mimolette cheese. It looks great but is as salty as an Atlantic wave in the face. The salt batters the vanilla dusting and the cheese and even the spud flavour to the floor.

Mercifully it gets better. The sweet spot is Trish’s exquisite wild salmon (“I caught it myself,” Monsieur Guilbaud tells her with an arched eyebrow). It has a seam of quivering barely cooked pink flesh running between two paler outer edges. It’s a taste that makes you glad to be alive in this room in this city at this time. The fish is served without a foam or a folderol, on a gorgeous leaf of brightest green York cabbage with a potato gnocchi and a fennell [sic] sauce.

Before this resounding hit, there’s a sesame-seared tuna slice sitting on bite-sized pieces of grapefruit and topped with a tangle of thinly sliced mange-tout and chilli. It’s a surprisingly simple starter for a two-star restaurant, where sesame seeds tend to only get a look in by being ironic or playful or fiendishly-disguised as meteor dust or outer-Hebridean sand. Here they’re just lightly toasted and sprinkled on the fish. My ravioli of confit tomato has a nice set of flavours, some lovely cherry tomatoes that are pops of sweet juice with perfect basil leaves. The dashi sauce doesn’t have any of the life-altering umami notes that you read about this Japanese broth having. I’m left looking to the cheese in the ravioli for a base note to batten down the lightness.

The second main course of roasted magret of duck is good, but decidedly chewy. I’m no fan of millionaire babyfood, the kind that feels like someone else has masticated it for you. But this is a step too far in the other direction.

Desserts are beautiful. A plate of green apple parfait, with white chocolate, pistachio ice-cream and raspberry looks like a sugar-spun solar system. My poached apricot has a lovely amaretto biscuit with perfect almond ice- cream. The petit fours do the mirror of the amuse bouche at the start and deliver tooth-aching hits of sugar.

It’s been more relaxed than I expected. The cloche (possibly the same one I blushed into a quarter of a century ago) reflects back an older but grinning rather than grimacing face. There has been nothing wrong with my food but nothing bell-ringingly right either. Perhaps the leap that takes you from good humoured to giddy requires a spendier visit, and maybe more booze. But I’m glad we came, not least because you can see the restaurant has weathered the years of inconspicuous consumption without dialling down its old school sense of occasion.

Lunch for two with two glasses of wine (Sancerre and a Nebbiolo) and two bottles of sparkling water comes to €146. It’s a surprise to leave feeling underwhelmed by the food in Ireland’s top restaurant. That’s reflected in this week’s mark out of 10. There is brilliant food to be had for this kind of money. I haven’t found it here.

The Verdict: 7/10

Restaurant Patrick Guildbaud, 21 Upper Merrion St, Dublin 2, tel: 01- 676 4192

Facilities: Swish

Music: None heard over our nattering

Food provenance: Locations but no producers named

Wheelchair access: Yes

Vegetarian options: No huge choice

The verdict: Nowhere else does occasion quite like this Dublin duchess